As a control of an induction motor, there is known a vector control for an induction motor, in which a three-phase AC current flowing through a stator is transformed into a two-axis orthogonal coordinate system in synchronization with a power supply angular frequency corresponding to a sum of a motor electric angular frequency and a slip frequency to generate an excitation current and a torque current, and the motor torque is controlled by adjusting the excitation current and the torque current.
When the slip angular frequency is controlled to be proportional to a ratio between the torque current and the rotor magnetic flux, the induction motor torque is proportional to a product between a rotor magnetic flux generated with a delay from the excitation current and a torque current orthogonal to the rotor magnetic flux. In addition, there is known a technique of providing a non-interference controller that cancels an interference term in advance in order to perform a control independently because the axes interfere with each other.
For example, in JP09-047097A, there is disclosed a technique of computing an interference voltage using a mathematical model by receiving an electric current command value as an input. In addition, in JP01-020688A, there is disclosed a technique of computing a non-interference voltage using a mathematical model by receiving a real electric current as an input.